Treating hydrocarbon oils



O. BEHIMER March 21, 1933.

TREATING HYDROCARBON OILS Filed Feb. 10, 1928 Smvemtoz (am flm $5951 an??? AM Patented Mar. 21, 1933 UNITED STATES PATENT OFFICE OTTO IBEHIMER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE TEXAS COMPANY, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE TREATING HYDROCARBON OILS Application filed February 10, 1928. Serial No. 253,261.

This invention relates to the distillation of hydrocarbon oils and has to do particularly with the distillation of oil under superatmospheric pressure.

In the cracking and distillation of hydrocarbon oils under pressure it has beensought to effect a fractionation of the evolved va-- pors, but difliculty has been encountered in carrying on an effective fractionation due to the pressure under which the operation has been carried on, and due also to the great temperature differential that must be had in the fractionating apparatus. Thus, it is common to introduce vapors from the cracking still to the fractionating apparatus at a temperature of about 750 F. to 850 F., while the overhead vapors are taken off at a temperature around 400 F. or 500 F., thus necessitating a temperature differential through the fractionating apparatus of some 300 F. or

. 400 F. Ordinarily fractionating equipment that may be satisfactorily used in fractionating fluids where the temperature differential between the bottom or hottest part of the column and the overhead stream is not so great, .cannot be satisfactorily used in the fractionation of oil vapors under high pressure and involving the great temperature differential that is ordinarily required in fractionating the evolved vapors from cracking stills. It is one of the objects of my inven-i tion to provide apparatus and methods of opsupply all of the cooling medium required for the fractionating tower to the top thereof in the conventional manner, but that best results can be obtained by supplying a limited amount of cooling to the top of the tower so as to thereby efiectively control the end point of the gasoline or other light distillate taken 03 in the overhead stream, and to supply additional cooling at points lower down in the tower or in the hotter portions thereof.

liquid thereby collects in the upper portions 1 of thetower. which results in cutting down the capacity of the tower, but when only a limitedamount of cooling is supplied to the top of the tower, and the rest of the required cooling distributed through the tower, the capacity of the tower is increased, or in other words, the rate of production of the light distillate desired is increased.

In accordance with my invention, a cooling medium is supplied to the upper part of the tower, preferably in the form of a distillate, 1n such quantity as to give the maximum yield of gasoline or like distillate of the desired end point and color, while additional .cooling required in the'lower or intermediate sections of the tower is supplied at distributed points therein;-

The distillates obtained in the cracking of hydrocarbon oils are very sensitive to color transformation, and great care must be exercised in supplying the proper cooling to the top of the tower so thata distillate of the desired color may be obtained. I have found that if the condensate admitted to the tower as a reflux medium be taken from storage,

that'such condensate is frequently impaired.

in color and causes impairment in color of the overhead distillate from the tower.. I have found that it is highly desirable to subject the overhead stream of vapors from the tower to rapid cooling, and to return to the tower the condensate desired as a reflux before the condensate has had an opportunity to rise in color. The quick cooling necessary to obtain best results cannot ordinarilyv be obtained by using oil, such as charging stock, in the ordinary type of reflux condensers, and I therefore prefer to cool the vapors with a liquid such as water capable of effecting a rapid heat exchange with the oil vapors. In carrying out this process of the invention the vapors from the fractionating column may be conducted-to a preliminary coil or other suitable heat exchange device adapted for rapidly cooling a portion of the evolved vapors to thereby produce the desired reflux for the top of the tower, or if desired, the' preliminary condenser coil may be omitted and the vapors passed directly to the final condenser coil in which the final gasoline or other light condensate is obtained, and a portion of this distillate, before it has had time to go 01f color, is admitted to the tower as a reflux medium.

I have found that while it is desirable to admit to "the upper part of the tower, such, for example, as the top tray thereof, a distillate having substantially the end point desired in the gasoline or final distillate, that nevertheless it is preferable to use a distillate which, although of substantially the same end point as the final product, contains a greater proportion of the heavier constituents and a less portion of the lighter eonstituents. Thus, it is advantageous to provide a trap at an intermediate point in the condenser coil and conduct condensate from this trap directly to the top tray of the tower. In this way a distillate is obtained by quick cooling, and may thus be introduced to the top tray before it has had an opportun ty to go off color, and furthermore, thls dlstlllate, although of substantially the same end pomt as that of the final condensate removed from the end of the condenser coil, has a different distillation curve from that of the final distillate, containing greater quantities of the heavier constituents and less quantitles of the lighter constituents than the final condensate.

The cooling supplied to the lower or intermediate sections of the fractionatmg column may be applied in various ways. The charging stock may well be used; thus charging stock may be introduced into the tower at an intermediate point or at selected points therein to thereby commingle with the fluids undergoing fractionation and produce the cooling required or the oharglng stock or other suitable cooling medium may be passed through pipes positioned in intermediate portions of the tower.

One process of my invention contemplates a special method of applying cooling to the lower or intermediate sections of the tower. Liquid is withdrawn from the tower at selected points and cooled, and the cooled liquid is then introduced into the tower at other points. My invention contemplates a. fractionating or rectifying apparatus in which liquid is withdrawn from a cooler section thereof and the withdrawn liquid cooled and put back into the tower in a hotter section thereof, and the invention has in view the provision of a fractionating or rectifying column in which liquid, is withdrawn at a selected'point or points in the tower, the liquid cooled, and returned to the column at a point or points therein below those from which it was withdrawn.

In order to more fully describe the invention, reference will now be had to the ac eompanying drawing which is a diagrammatic sectional elevation of an apparatus constructed in accordance with the invention and constituting an embodiment thereof.

In the drawing a heating coil 10 mounted in a furnace 11, is connected by transfer line 12 to a still or converter 13. No heating means is shown for the still since the still may be insulated and maintained at the proper temperature for cracking and distillation, by means of the highly heated oil discharged through the transfer line 12, although if desired, the still 13 may be provided with suitable heating means. The still is equipped with a draw-oil line 14 for removing liquid or residue.

A vapor line 15 extends from the still 13 to a rectifying orfraetionating tower 16. The fraetionating equipment illustrated is of the bubble tower type being provided with a plurality of bubble trays 17. The detailed construction of the trays is not indicated, but it is to be understood that the trays may in elude the usual Vaporizers with superposed bubble caps. and with liquid downflow pipes, so that efficient contact may be had between the upwardly rising vapors andthe downfiowing liquid. It is convenient to arrange the bubble trays in several nests or sections as indicated. From the top tray of each of the several nests a pipe 18 is shown which is arranged to draw liquid from the bubble tray. Each of the pipes 18 communicates with a coil 19 positioned in a cooling chamber 20 \part of the tower. The several cooling chambers 20 are shown as being supplied with charging stock as a cooling medium; thus a pump 23 is arranged to draw oil from a suitable source and force the oil through a pipe 24 to the upper chamber 20. Pipes 2d interconnect the several chambers 20 so that the, charge may be passed successively through the chambers. If desired,other coolingmeans may be used for supplying the necessary cooling to the coils 19. but the arrangement illustrated is a novel way of utilizing the charging stock as a cooling medium in an advantageous manner. A pipe 25 conducts the charge from the bottom chamber 20 to the coil 10. A heat exchanger may be interposed in the line 25 arranged to utilize liquid withdrawn from the still 13 as a heating medium to further heat the charge before it is admitted to the coil 10. If desired, the outlet from the bottom chamber 20 may extend to a coil into the bottom of the fractionating tower 16 which coil may be connected to the heating coil 10 or the outlet from the lower chamber 20 may discharge directly into the bottom of the fractionating chamber as, for example, by means of a branch pipe 25a extending from'the pipe 25 to the tower 16 to thus discharge liquid over the bafiles 22. A pipe 26 is provided for removing liquid from the bottom of the fractionating column to a pump 27 by which the oil is forced through a line 28 to the coil 10.

A vapor line 29 extends from the fractionating tower 16 to a condenser coil 30 located in a condenser box 31 provided with an inlet pipe 32 for admitting water or other suitable cooling medium, and an outlet pipe 33 for withdrawing the liquid. An outlet line 34 extends from the condenser coil to a receiving drum 35 provided with a gas outlet 36 and a condensate outlet 37.

A trap 38 is indicated in an intermediate portion of the condenser coil 30 and is adapted to separate out liquid or condensate from the vapors and gases. A condensate line 39 conducts condensate from a trap 38 to a cooling coil 40 which is provided with an outlet pipe 41 extending to a pump 42 by means of which the cooled condensate is pumped through a line 43 to the top of the tower 16 or more specifically to the top tray of the tower. A by-pass line 44 is provided so that in case it is not desired to use the cooling coil 40 it may be by-passed. If desired the trap 38 may be omitted and the pump 42 arranged to draw oil from the line 34 or from the receiving drum 35, but in such-case the distillate thus pumped to the top tray of the fractionating tower 16 is of course the same as that of the final distillate desired, having not only the same end point but also the same distillation curve, and in cases where it is desired to introduce to the top tray of the fractionating tower a distillate having a difierent distillation curve, although having the same end point as that of the final distillate desired, it is desirable to trap out this distillate at an intermediate point in the cooling coil 30 to thereby obtain a condensate having the desired characteristics.

In practicing the invention with the appa ratus thus illustrated a suitable charging stock is introduced by the pump 23 and preheated by passage through the several chambers 20. The preheated oil is then passed through the pipe 25 to the coil 10 wherein the oil is preferably raised to a cracking temperature after which it is discharged into the still 13 wherein a body of oil is maintained under cracking temperatures and pressures. The evolved vqpors are taken ofi through vapor line 15 an passedthence into the fractionating column 16. The liquid collecting at the bottom of the fractionating tower is continuously cycled. back to the coil 10 by means of the pump 27 and the overhead vapor fraction is taken ofi through the vapor line 29, condensed in the coil 30, and collected In the receiver 35. The pump 42 is arranged to introduce the proper quantity of reflux condensate to the top of the tower to thereby control the end point of the vapor fraction passed into the pipe 29 and collected as a condensate in the receiver 35. By withdrawing liquid cooled in the trap 38 and pumping it back immediately to the top tray of the tower before the liquid has had time to go off color, the necessary cooling for the top of the tower is supplied without thereby impairing the color of the distillate drawn off through the vapor line 29 and collected in the receiver 35. The rest of the cooling required for the tower is furnished by the withdrawal of liquid through the pipes 18, the cooling of this liquid in the coils 19, and the return to the tower of the cooled liquid through the pipes 21. By having the cooling thus distributed through the tower, suflicient cooling is thereby supplied without having an excessive quantity of liquid in the upper sections of the tower.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

What I claim is:

1. Apparatus for treating hydrocarbon oil comprising in combination means for raising hydrocarbon oil to a cracking temperature, means for separating vapors from the resulting cracked products, a fractionating tower for treating said vapors, said tower having in the upper portion thereof a plurality of bubble trays and in the lower portion thereof a plurality of bafile plates, means for introducing said vapors into the lower portion of said tower below the level of said baflle plates, means for removing a desired li ht distillate from said tower, means for- 'w1thdrawing a reflux condensate from said tower, cooling said condensate and returning it to a point just above said baflie plates, and means for recycling reflux condensate from the bottom of said tower through said means first mentioned.

2. Apparatus for treating hydrocarbon oil comprising in combination means for raising hydrocarbon oil to a cracking temperature, means for separating vapors from the resulting cracked products, a fractionating tower for treating said vapors, said tower having in the upper portion thereof a plurality of bubble trays. and in the lower portion thereof a plurality of baflie plates, means for introducing said vapors into the lower portion of said tower below the level of said I baflle plates, means for removing a desired Gil light distillate from said tower and means for withdrawing a reflux condensate from said tower, cooling said condensate and returning it to a point just above said baflie plates.

3. Apparatus for treating hydrocarbon oil comprising in combination means for raising 1 hydrocarbon oil to a cracking temperature, means for separating vapors from the resulting cracked products, a fractionatingtower for treating said vapors, said tower having in the upper portion there of a plurality of bubble trays and in the lower portion thereofa plurality of baflle plates, means for introducing said vapors into the lower portion of said tower below the level of said bafile plates, means for removing a desired light distillate from said tower, means for withdrawing a reflux condensate from said tower, means for cooling the withdrawn condensate by indirect heat exchange with fresh charging stock for the apparatus, and means for returning the cooled condensate to a point just above said bafile plates.

4. Apparatus for treating hydrocarbon oil comprising in combination means for raising hydrocarbon oil to a cracking temperature,

means for separating vapors from the resulting cracked products, a fractionating tower for treating said vapors, said tower having in the upper portion thereof a plurality of bubble trays and in the lower portion thereof a plurality of bafiie plates, means for introducing said vapors into the lower portion of said tower below the level of said baflie plates, means for removing a desired light distillate from said tower, a reflux condensate from an intermediate point of said upper portion of said tower, cooling said condensate and returning it to a point just above said bafile plates. OTTO BEHIMER.

and means for withdrawing 

